In school, we are brought up to learn direct recovery practices. The way this is done with most systems is to do a vapor recovery to push into our cylinder. This method is fairly inefficient and creates a lot of heat in the recovery cylinder. We have all been there trying to recover a R410a split system or RTU, it’s barely moving refrigerant because your tank is so hot you can barely touch it and pushing 400psig at the tank.
While direct recovery procedures are not avoidable, scale these issues to recovering the volume of a water cooled chiller. There are two ways to improve the recovery process. The first major way is to use a subcooler inline between your recovery machine and your cylinder. Adding this component will remove the heat of compression generated by pumping the refrigerant through the recovery machine. A big hack/secret to really fast recovery is to keep your pressure differential across your pump as low as possible. A well designed and implemented subcooler will keep your cylinder temperature low, allowing maximum volume through the pump. While there are braze plate subcoolers out there the most common are copper coil subcoolers. These are spooled coils that sit in a bucket of water, some tech’s add ice, to remove the heat. You can make your own and working on large equipment, I recommend that option as the pre produced ones are too small for industrial applications.
The second improvement is becoming comfortable pumping liquid refrigerant. Not all standard recovery machines can move liquid but the two I personally recommend are, Appion G5Twin and NAVAC NRDC4M. The NRDC4M has become my go to pump for some time now. There are industrial pump out machines that are great as well but most of them that I'm aware of don’t pump direct liquid. To pump liquid you will at minimum remove all restrictions from your hoses including things like core depressors. It is best to get larger diameter hoses to prevent pump shuttering, like 3/8 hoses.
There is another modified version of this we can discuss but that will be for another day! Get in depth chiller training and support from a chiller community by enrolling today at chilleracademy.com.
Now to put all of that together. The bottom of the evaporator will have a recovery port, connect a hose from this port to the inlet of your recovery machine. Next connect a hose from the outlet of your recovery machine to the inlet of your subcooler. From the outlet of the subcooler connect a hose to the liquid port of the cylinder. Be sure to flow water through your barrels to protect from freezing and use a scale to safely fill your cylinder.
